On the use of sweeping jets to augment the lift of a λ-wing

Super-critical airfoils that are optimized for high speed subsonic flight require complex auxiliary high-lift systems for take-off and landing. A lambda wing model, based on such an airfoil, but containing simple flaps augmented by sweeping jet actuators, was constructed and tested. The purpose of these tests was to assess the efficacy of this method of separation control on a realistic wing configuration. Force and pressure measurements were carried out on this wing as well as surface flow visualization that used tufts and china clay. The strength of this actuation was altered and its effects were assessed. The orientation of the actuators was also altered for the outboard flap. The first flap had actuators aligned with the free stream while the second one had them parallel to the leading-edge that was swept back at 40°. The actuation from the second set of flaps turned out to be more effective because it affected only the decelerating flow component and no momentum was wasted on span-wise flow. These observations reaffirmed the ideas embedded in the boundary layer "independence principle" for large aspect ratio swept back cylinders.